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Abstract

In tomographic scanning (TOSCA) imaging, light from a scene is focused onto a reticle mask using conical scan optics, and collected on a single element detector. Alternatively, one or several detectors replace the reticle. Tomographic processing techniques are then applied to the one-dimensional signal to reproduce a two-dimensional image. The TOSCA technique is presented in detail, including its mathematical foundations and some of its limitations. It is shown how TOSCA imaging can be used in a multispectral configuration, and compares well with more conventional alternatives both in simplicity and performance. Examples of image reconstruction using TOSCA techniques are shown.

Geometrical considerations. (a) Scene masked by circular aperture and knife-edge. The latter is defined by the line Li and the normal unit vector ki. Also indicated is ri, a point along Li. The indicated scan velocity gives a positive scan speed and an increasing signal. The terms in equation (4) are due to scene variations and the moving knife-edge. (b) When reconstructing an image using discrete samples, the frequencies of a shaded area are represented by the value of its centre point. The sampled value is therefore multiplied by the area it represents in Fourier space. The two darkest patches are represented by the origin in the given scan. The angles are in the range [0,π[, and the frequency values include both positive and negative values.

Tables (1)

Table 1. General parameters governing noise performance of various detector configurations for a single image frame, normalized to the 2-dimensional array detector. A channel is here a pixel in the reconstructed image, and n denotes the array length or diameter, as well as the number of independent angular scans.

Metrics

Table 1.

General parameters governing noise performance of various detector configurations for a single image frame, normalized to the 2-dimensional array detector. A channel is here a pixel in the reconstructed image, and n denotes the array length or diameter, as well as the number of independent angular scans.